Protected prong file fastener and method of manufacture

Abstract

A prong style file fastener and the method of manufacture is disclosed which has a protective element to prevent damage to paper documents and personal injury. In one embodiment, the prongs of the fastener are covered with a heat shrinkable sheath. In another, the prongs are overcoated with a powder coating which is melted thereon. A method of applying the sheath to the prongs uses a pair of jaws or V-shaped surface to drive the sheath onto the prongs.

The invention claimed is: 
     
       1. A machine for applying a heat shrinkable tubing on a generally planar paper fastener prong, comprising:
 a. tubing supply driver including first and second drive wheels each having a circumferential recess in their outer periphery, said drive wheels having their circumferential edges located adjacent each other, said recess together defining a space just smaller than the outer circumference of the tubing; said driver being actuatable to drive said tubing laterally onto said prong; 
 b. a pusher for further sliding the tubing into a final position on the prong; said pusher including first and second opposing jaws, at least one of said jaws including a pivotal arm; and 
 c. a reciprocating arm and lateral driver attached to a link and capable of sequentially moving the jaws between open and closed positions and then further moving the jaws laterally, thereby driving, through said link, the jaws between open and closed positions and then laterally toward said prong, wherein, in said closed position, said jaws engage said tubing to drive it onto said prong. 
 
     
     
       2. The machine of  claim 1 , wherein said opposing jaws are generally planar and include a plurality of teeth to engage said tubing. 
     
     
       3. The machine of  claim 1 , wherein said machine is adapted to act on a prong which is tapered from a base to a distal free end. 
     
     
       4. An apparatus for applying a shrinkable tube to a plurality of spaced apart generally planar prong elements, comprising:
 a. first and second opposing jaw members having inner opposing faces each having gripping portions thereon; 
 b. at least one of said members having a pivot distant from said gripping portions; 
 c. a three point link pivotally connected to said pivot at one point, to a stationary member at a second point and to a reciprocating driver at a third point; 
 d. said reciprocating driver capable of imparting movement into said link and thereby to said gripping portions via said link to bring said jaw members together thereby sufficiently engaging a tube disposed on a generally planar prong; and 
 e. a lateral driver connected to said link and actuated when said jaw members engage said tube, to further drive the jaw members laterally and push the engaged tube along the prong. 
 
     
     
       5. The apparatus of  claim 4  wherein said link is a chain link pivotally connected at one end to the reciprocating driver. 
     
     
       6. The apparatus of  claim 4  wherein said lateral driver is connected to a mount upon which also includes the link and jaws, so that when the lateral driver moves, the link and the jaws are likewise moved. 
     
     
       7. The apparatus of  claim 4  further including a pair of pinch rollers sized to snugly receive a length of said tubing and drive it on to the prong. 
     
     
       8. The apparatus of  claim 7  wherein said pinch rollers include a pair of rollers contacting on their peripheral edge and wherein their peripheral edge includes a recess to receive said tubing.